Structural health monitoring (SHM) is essential for key components in load-bearing structures. It characterizes the current material state and enables condition-based maintenance. Aircraft SHM demands lightweight transducers having a small footprint. In this paper, linear phased array transducers composed of piezoelectric fiber composite elements to control generation of ultrasonic guided waves are shown to have excellent potential for aircraft SHM. Ultrasonic guided waves are sensitive to diverse types of degradation and can effectively monitor reasonably large regions. The ability of the transducers to generate a preselected dominant guided wave mode over a reasonably broad frequency range is documented and in good agreement with model predictions for an aluminum plate and a composite laminate. In addition, the transducers can determine the modal content of received wave packets. These two capabilities enable the use of modal amplitude ratios or mode conversion for reliable SHM. Furthermore, the transducers enable scanning of subdomains within the dispersion curve space when material parameters, and therefore the dispersion curves themselves, are unknown.